Am I responsible for tenant’s clogged bathtub drain?

[Alexander Rodriguez]

I bought a 3 unit up-down building about 1.5 years ago. One thing that I fixed was the ceiling in the bathroom of the second floor tenant. One month ago I made an inspection and tenant stated that there are no drain issues. The tenant signed the inspection. Today, I got a call from the tenant stating that since they fixed the ceiling the bathtub drain has been slow moving and is now clogged because they never covered the drain, according to them. I told them I would take a look at it.

However, I find it hard to believe that it can be caused by something that happened 1.5 years ago and they never reported any issues. I stated in the co tract that they are responsible for clogged drains if it’s their fault. That’s why I believe they claim that it’s my fault. I’m thinking that I don’t have a way to show that it’s their fault. If I hire a plumber and make them pay, will they know what caused the clog?

Or is there any chance that it could be caused by something that is not their fault? The other units don’t have drain issues, which makes me think that the main line is fine, so the clog must be on their end. Is my reasoning right?